This trial will evaluate the safety and efficacy of rufinamide as adjunctive therapy, relative to placebo, in adults with inadequately controlled partial seizures. There purpose of this trial is to provide data in support of an adjunctive therapy indication for rufinamide in adults. For its secondary objective, the population pharmacokinetic profile of rufinamide will be explored The trial consists of 3 phases: baseline, double blind, and long term extension.